Sleep inducing agent

ABSTRACT

A sleep-inducing preparation which comprises as an effective ingredient a prostaglandin derivative represented by the formula:                    
     wherein X is a halogen atom, Y is a group represented by (CH 2 ) m , a cis-vinylene group or a phenylene group, Z is an ethylene group, a trans-vinylene group, OCH 2  or S(O) n CH 2 , R 1  is a C 3-10  cycloalkyl group, a C 3-10  cycloalkyl group substituted with C 1-4  alkyl group(s), a C 4-13  cycloalkylalkyl group, a C 5-10  alkyl group, a C 5-10  alkenyl group, a C 5-10  alkynyl group or a bridged cyclic hydrocarbon group, R 2  is a hydrogen atom, a C 1-10  alkyl group or a C 3-10  cycloalkyl group, m is an integer of 1 to 3, and n is 0, 1 or 2, a pharmaceutically acceptable salt thereof or a hydrate thereof.

This application is a 371 of PCT/JP99/02123 filed May 25, 1994.

TECHNICAL FIELD

The present invention relates to a sleep-inducing preparation comprising a prostaglandin derivative as an effective ingredient.

BACKGROUND ART

Since prostaglandin (hereinafter referred to as “PG”) exhibits various important physiological actions in a trace amount, the syntheses of the derivatives from natural PGs and the biological activities have been investigated with the intention of a practical use as medicines and have been reported in many literatures.

Particularly, PGs have been reported on the various central nervous actions and have been clarified as to the intracerebral content, biosynthesis, metabolic pathway, their intracerebral localizations and changes with growth or aging, and there has been taken an interest in the relation of PGs with sleep and wake. Among them, PGD₂ has been known as an intracerebral humoral factor which controls the occurrence or maintenance of sleep, and it was made clear that the sleep induced by PGD₂ in monkeys is undistinguished from the spontaneous natural sleep in brain wave or behavior (Proc. Natl. Acad. Sci. USA, vol. 85, pp. 4082-4086 (1988)), therefore this compound is expected as a compound having a novel sleep-inducing action.

However, PGD₂ derivatives including PGD₂ are presently unpractical due to the problems concerning the effect and the stability as a drug.

DISCLOSURE OF THE INVENTION

As a result of the extensive studies, the present inventors have found that the prostaglandin derivatives having a triple bond between the 13- and 14-position represented by the following formula (I) have a characteristic sleep-inducing action, and thereby the present invention has been accomplished.

That is, the present invention is directed to a sleep-inducing preparation which comprises as an effective ingredient a prostaglandin derivative represented by Formula (I):

wherein X is a halogen atom, Y is a group represented by (CH₂)_(m), a cis-vinylene group or a phenylene group, Z is an ethylene group, a trans-vinylene group, OCH₂ or S(O)_(n)CH₂, R¹ is a C₃₋₁₀ cycloalkyl group, a C₃₋₁₀ cycloalkyl group substituted with C₁₋₄ alkyl group(s), a C₄₋₁₃ cycloalkylalkyl group, a C₅₋₁₀ alkyl group, a C₅₋₁₀ alkenyl group, a C₅₋₁₀ alkynyl group or a bridged cyclic hydrocarbon group, R² is a hydrogen atom, a C₁₋₁₀ alkyl group or a C₃₋₁₀ cycloalkyl group, m is an integer of 1 to 3, and n is 0, 1 or 2, or a pharmaceutically acceptable salt thereof.

Further, the present invention is directed to a sleep-inducing preparation which comprises as an effective ingredient a prostaglandin derivative represented by Formula (I) wherein X is a chlorine atom or a bromine atom, Y is a group represented by (CH₂)_(m) or a cis-vinylene group, Z is an ethylene group, a trans-vinylene group, OCH₂ or S(O)_(n)CH₂, R¹ is a C₃₋₁₀ cycloalkyl group or a C₄₋₁₃ cycloalkylalkyl group, R² is a hydrogen atom or a C₁₋₁₀ alkyl group, m is an integer of 1 to 3, and n is 0, 1 or 2, or a pharmaceutically acceptable salt thereof.

Furthermore, the present invention is directed to a sleep-inducing preparation which comprises as an effective ingredient a prostaglandin derivative represented by Formula (I) wherein X is a chlorine atom or a bromine atom, Y is a group represented by (CH₂)_(m) or a cis-vinylene group, Z is OCH₂, R¹ is a C₃₋₁₀ cycloalkyl group or a C₄₋₁₃ cycloalkylalkyl group, R² is a hydrogen atom or a C₁₋₁₀ alkyl group, and m is an integer of 1 to 3, or a pharmaceutically acceptable salt thereof.

Still furthermore, the present invention is directed to a sleep-inducing preparation which comprises as an effective ingredient a prostaglandin derivative represented by Formula (I) wherein X is a chlorine atom or a bromine atom, Y is a group represented by (CH₂)_(m) or a cis-vinylene group, Z is SCH₂, R¹ is a C₃₋₁₀ cycloalkyl group or a C₄₋₁₃ cycloalkylalkyl group, R² is a hydrogen atom or a C₁₋₁₀ alkyl group, and m is an integer of 1 to 3, or a pharmaceutically acceptable salt thereof.

Still furthermore, the present invention is directed to a sleep-inducing preparation which comprises as an effective ingredient a prostaglandin derivative represented by Formula (I) wherein Y is a group represented by (CH₂)_(m), Z is SCH₂, R¹ is a C₃₋₁₀ cycloalkyl group, R² is a hydrogen atom or a C₁₋₁₀ alkyl group, and m is an integer of 1 to 3, or a pharmaceutically acceptable salt thereof.

Still furthermore, the present invention is directed to the above-mentioned prostaglandin derivative or the pharmaceutically acceptable salt for use as an ingredient for sleep-inducing preparation.

Still furthermore, the present invention is directed to a method for sleep-inducing comprising administering a pharmaceutically effective amount of the above-mentioned prostaglandin derivative or the pharmaceutically acceptable salt to a human.

In the present invention, the halogen atom refers to a fluorine atom, a chlorine atom, a bromine atom or an iodine atom.

Examples of the C₃₋₁₀ cycloalkyl group are a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group and a cycloheptyl group.

Examples of the C₃₋₁₀ cycloalkyl group substituted with C₁₋₄ alkyl group(s) are a methylcyclopropyl group, a methylcyclohexyl group and an ethylcyclohexyl group.

Examples of the C₄₋₁₃ cycloalkylalkyl group are a cyclopropylmethyl group, a cyclobutylmethyl group, a cyclopentylmethyl group, a cyclopentylethyl group, a cyclohexylmethyl group, a cyclohexylethyl group and a cycloheptylmethyl group.

The C₅₋₁₀ alkyl group refers to a straight or branched alkyl group, and examples thereof are a pentyl group, a hexyl group, a heptyl group, an octyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 1-methylhexyl group, a 2-methylhexyl group, a 2,4-dimethylpentyl group, a 2-ethylpentyl group, a 2-methylheptyl group, a 2-ethylhexyl group, a 2-propylpentyl group, a 2-propylhexyl group and a 2,6-dimethylheptyl group.

The C₅₋₁₀ alkenyl group refers to a straight or branched alkenyl group, and examples thereof are a 3-pentenyl group, a 4-hexenyl group, a 5-heptenyl group, a 4-methyl-3-pentenyl group, a 2,4-dimethylpentenyl group, a 6-methyl-5-heptenyl group and a 2,6-dimethyl-5-heptenyl group.

The C₅₋₁₀ alkynyl group refers to a straight or branched alkynyl group, and examples thereof are a 3-pentynyl group, a 3-hexynyl group, a 4-hexynyl group, a 1-methylpent-3-ynyl group, a 2-methylpent-3-ynyl group, a 1-methylhex-3-ynyl group and a 2-methylhex-3-ynyl group.

Examples of the bridged cyclic hydrocarbon group are a bornyl group, a norbornyl group, an adamantyl group, a pinanyl group, a thujyl group, a caryl group and a camphanyl group.

The C₁₋₁₀ alkyl group for R² refers to a straight or branched alkyl group, and examples thereof are a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, a 2-ethylpropyl group, a hexyl group, an isohexyl group, a 1-ethylbutyl group, a heptyl group, an isoheptyl group, an octyl group, a nonyl group and a decyl group.

Examples of the pharmaceutically acceptable salt are salts with alkali metal (e.g. sodium or potassium), alkali earth metal (e.g. calcium or magnesium), ammonia, methylamine, dimethylamine, cyclopentylamine, benzylamine, piperidine, monoethanolamine, diethanolamine, monomethylmonoethanolamine, tromethamine, lysine, a tetraalkyl ammonium and tris(hydroxymethyl)aminomethane.

According to the sleep-inducing preparation of the present invention, in view of the sleep-inducing effect, Y is preferably an ethylene group or cis-vinylene group, Z is preferably OCH₂ or SCH₂, and R¹ is preferably a cycloalkyl group in Formula (I) of the prostaglandin derivatives as the effective ingredient.

Some of the compounds of Formula (I), according to the present invention, are known in WO94/02457, WO94/08959, Japanese Patent Kokai Hei-6-192218, Japanese Patent Kokai Hei-7-242622, Japanese Patent Kokai Hei-7-242623, Japanese Patent Kokai Hei-7-233144, Japanese Patent Kokal Hei-7-285929, Japanese Patent Kokai Hei-8-208599, Japanese Patent Kokal Hei-7-233143, Japanese Patent Kokal Hei-9-286775, Japanese Patent Kokai Sho-58-8059, Japanese Patent Kohyo Sho-60-501813 and Japanese Patent Kohyo Sho-60-500787.

On the other hand, the compounds wherein Z is S(O)CH₂ and S(O)₂CH₂ can be prepared by a reaction of the compounds wherein Z is SCH₂ using an oxidant such as sodium metaperiodide in a solvent such as methanol.

According to the present invention, representative compounds of Formula (I) are described as follows:

TABLE 1 (I)

Compound No. X Y Z R¹ R² 8-position 15-position Compound 1 β-Cl CH═CH OCH₂ cyclohexyl tert-butyl α α Compound 2 β-Cl CH═CH OCH₂ cyclohexyl methyl α α Compound 3 β-Cl CH═CH OCH₂ cyclohexyl methyl α β Compound 4 β-Cl CH═CH OCH₂ cyclohexyl hydrogen α α Compound 5 β-Cl CH═CH OCH₂ cyclohexyl hydrogen α β Compound 6 β-Cl CH═CH OCH₂ cyclohexyl hydrogen α α Compound 7 β-Br CH═CH OCH₂ cyclohexyl hydrogen α α Compound 8 β-Br CH═CH OCH₂ cyclohexyl hydrogen β α Compound 9 F CH═CH OCH₂ cyclohexyl hydrogen α α Compound 10 β-Br CH═CH OCH₂ cyclopentyl hydrogen α α Compound 11 β-Br CH═CH OCH₂ cycloheptyl hydrogen α α Compound 12 β-Br CH═CH OCH₂ cyclopentylmethyl hydrogen α α Compound 13 β-Br CH═CH OCH₂ cyclohexylmethyl hydrogen α α Compound 14 β-Cl CH═CH SCH₂ cyclohexyl tert-butyl α α Compound 15 β-Cl CH═CH SCH₂ cyclohexyl hydrogen α α Compound 16 β-Cl CH₂CH₂ OCH₂ cyclohexyl tert-butyl α α Compound 17 β-Cl CH₂CH₂ OCH₂ cyclohexyl methyl α α Compound 18 β-Cl CH₂CH₂ OCH₂ cyclohexyl methyl α β Compound 19 β-Cl CH₂CH₂ OCH₂ cyclohexyl hydrogen α α Compound 20 β-Cl CH₂CH₂ OCH₂ cyclohexyl hydrogen α β Compound 21 β-Cl CH₂CH₂ OCH₂ cyclopentyl hydrogen α α Compound 22 β-Cl CH₂CH₂ OCH₂ cycloheptyl hydrogen α α Compound 23 β-Cl CH₂CH₂ OCH₂ cyclopentylmethyl hydrogen α α Compound 24 β-Cl CH₂CH₂ OCH₂ cyclohexylmethyl hydrogen α α Compound 25 α-Cl CH₂CH₂ OCH₂ cyclohexyl hydrogen β α Compound 26 β-Br CH₂CH₂ OCH₂ cyclohexyl hydrogen α α Compound 27 α-Br CH₂CH₂ OCH₂ cyclohexyl hydrogen α α Compound 28 F CH₂CH₂ OCH₂ cyclohexyl hydrogen α α Compound 29 β-Cl CH₂CH₂ SCH₂ cyclohexyl tert-butyl α α Compound 30 β-Cl CH₂CH₂ SCH₂ cyclohexyl methyl α α Compound 31 β-Cl CH₂CH₂ SCH₂ cyclohexyl methyl α β Compound 32 β-Cl CH₂CH₂ SCH₂ cyclohexyl hydrogen α α Compound 33 β-Cl CH₂CH₂ SCH₂ cyclohexyl hydrogen β α Compound 34 β-Cl CH₂CH₂ SCH₂ cyclohexyl hydrogen α β Compound 35 β-Cl CH₂CH₂ SCH₂ cyclopentyl hydrogen α α Compound 36 β-Cl CH₂CH₂ SCH₂ cyclopentylmethyl hydrogen α α Compound 37 β-Cl CH₂CH₂ SCH₂ cyclohexylmethyl hydrogen α α Compound 38 α-Cl CH₂CH₂ SCH₂ cyclohexyl hydrogen α α Compound 39 β-Br CH₂CH₂ SCH₂ cyclohexyl hydrogen α α Compound 40 α-Br CH₂CH₂ SCH₂ cyclohexyl hydrogen α α Compound 41 F CH₂CH₂ SCH₂ cyclohexyl hydrogen α α Compound 42 β-Cl CH₂CH₂ OCH₂ 2-methyl-1-hexyl hydrogen α α Compound 43 β-Cl CH₂CH₂ SCH₂ 2-methyl-1-hexyl hydrogen α α Compound 44 β-Cl CH₂CH₂ OCH₂ 2,6-dimethyl-5-heptenyl hydrogen α α Compound 45 β-Cl CH₂CH₂ SCH₂ 2,6-dimethyl-5-heptenyl hydrogen α α Compound 46 β-Cl o-interphenylene OCH₂ cyclohexyl hydrogen α α Compound 47 β-Cl m-interphenylene OCH₂ cyclohexyl hydrogen α α Compound 48 β-Cl p-interphenylene OCH₂ cyclohexyl hydrogen α α Compound 49 β-Cl o-interphenylene SCH₂ cyclohexyl hydrogen α α Compound 50 β-Cl m-interphenylene SCH₂ cyclohexyl hydrogen α α Compound 51 β-Cl p-interphenylene SCH₂ cyclohexyl hydrogen α α Compound 52 β-Cl CH₂CH₂ CH₂CH₂ cyclohexyl methyl α α Compound 53 β-Cl CH₂CH₂ CH₂CH₂ cyclohexyl hydrogen α α Compound 54 β-Cl CH₂ CH₂CH₂ cyclohexyl hydrogen α α Compound 55 β-Cl CH₂CH₂ CH₂CH₂ cyc1opentyl hydrogen α α Compound 56 β-Cl CH₂CH₂ CH₂CH₂ cycloheptyl hydrogen α α Compound 57 β-Cl CH₂CH₂ CH₂CH₂ cyclopentylmethyl methyl α α Compound 58 β-Cl CH₂CH₂ CH₂CH₂ cyclopentylmethyl hydrogen α α Compound 59 β-Cl CH₂CH₂ CH₂CH₂ cyclohexylmethyl methyl α α Compound 60 β-Cl CH₂CH₂ CH₂CH₂ cyclohexylmethyl hydrogen α α Compound 61 β-Cl CH₂CH₂ CH₂CH₂ 2-methyl-1-hexyl methyl α α Compound 62 β-Cl CH₂CH₂ CH₂CH₂ 2-methyl-1-hexyl hydrogen α α Compound 63 β-Cl CH₂CH₂ CH₂CH₂ 2,6-dimethyl-5-heptenyl methyl α α Compound 64 β-Cl CH₂CH₂ CH₂CH₂ 2,6-dimethyl-5-heptenyl hydrogen α α Compound 65 β-Cl CH₂CH₂ CH₂CH₂ 1-methyl-3-hexynyl methyl α α Compound 66 β-Cl CH₂CH₂ CH₂CH₂ 1-methyl-3-hexynyl hydrogen α α Compound 67 β-Cl CH₂CH₂ CH═CH cyclohexyl tert-butyl α α Compound 68 β-Cl CH₂CH₂ CH═CH cyclohexyl Isopropyl α α Compound 69 β-Cl CH₂CH₂ CH═CH cyclohexyl methyl α α Compound 70 β-Cl CH₂CH₂CH₂ CH═CH cyclohexyl methyl α α Compound 71 β-Cl CH₂CH₂ CH═CH cyclohexyl hydrogen α α Compound 72 β-Cl CH₂CH₂CH₂ CH═CH cyclohexyl hydrogen α α Compound 73 β-C1 CH₂CH₂ CH═CH cyclopentyl methyl α α Compound 74 β-Cl CH₂CH₂ CH═CH cyclopentyl hydrogen α α Compound 75 β-Cl CH₂CH₂ CH═CH cycloheptyl methyl α α Compound 76 β-Cl CH₂CH₂ CH═CH cycloheptyl hydrogen α α Compound 77 β-Cl CH₂CH₂ CH═CH cyclopentylmethyl methyl α α Compound 78 β-Cl CH₂CH₂ CH═CH cyclopentylmethyl hydrogen α α Compound 79 β-Cl CH₂CH₂ CH═CH cyclohexylmethyl methyl α α Compound 80 β-Cl CH₂CH₂ CH═CH cyclohexylmethyl hydrogen α α Compound 81 β-C1 CH₂CH₂ CH═CH 2-methyl-1-hexyl methyl α α Compound 82 β-Cl CH₂CH₂ CH═CH 2-methyl-1-hexyl hydrogen α α Compound 83 β-Cl CH₂CH₂ CH═CH 2,6-dimethyl-5-heptenyl methyl α α Compound 84 β-Cl CH₂CH₂ CH═CH 2,6-dimethyl-5-heptenyl hydrogen α α Compound 85 β-Cl CH₂CH₂ CH═CH 1-methyl-3-hexynyl methyl α α Compound 86 β-Cl CH₂CH₂ CH═CH 1-methyl-3-hexynyl hydrogen α α

The compounds in the present invention can be administered orally or parenterally such as intravenously or nasally. For example, they can be administered orally in the form such as tablets, dusting powders, granules, powders, capsules, solutions, emulsions or suspensions, each of which can be prepared according to conventional methods. As the dosage forms for intravenous administration, there are used aqueous or non-aqueous solutions, emulsions, suspensions or solid preparations to be dissolved in a solvent for injection immediately before use. Furthermore, nasal administration can be performed by spraying quantitatively a solution or a powder (hard capsules) containing the drug into the nasal cavity by use of a dedicated nasal dropper or sprayer. The compounds in the present invention can be formulated into the form of the inclusion compounds with α-, β- or γ-cyclodextrin, or methylated cyclodextrin. The dose is varied by the age, body weight, etc., but it generally is from 1 ng to 1 mg/day per adult.

INDUSTRIAL APPLICABILITY

The present invention makes it possible to provide a sleep-inducing preparation which is sufficiently effective and remarkably stable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing which shows a result of the sleep-inducing action by administration of Compound 32 according to Experiment 2, and

FIG. 2 is a drawing which shows a result of the sleep-inducing effect by administration of PGD₂ according to Experiment 2.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is illustrated more particularly by the following examples and experiments.

EXAMPLE 1

With 1 mg of Compound 4 synthesized according to the method described in WO94/02457 was combined 30 mg of calcium carbonate (light), thereby a hard capsule preparation was obtained.

EXAMPLE 2

In 1 ml of an isotonic phosphate buffer (pH 7.4) was dissolved 10 mg of Compound 32 synthesized according to the method described in WO94/02267, thereby a nasal drop preparation was obtained.

EXAMPLE 3

In 1 ml of an isotonic phosphate buffer (pH 7.4) was dissolved 10 mg of Compound 23 synthesized according to the method described in WO94/08959, thereby a nasal drop preparation was obtained.

Experiment 1

[Sleep-inducing Test By Nasal Administration]

Method

Nine male rhesus monkeys weighing about 6 kg were divided into groups of 3 monkeys. In order to homogeneously spray drugs into the nasal cavity, calcium carbonate and sofalcone were used as carriers, and Test drug 1 (a hard capsule preparation containing 1 mg of Compound 4 and 30 mg of calcium carbonate (light)), Test drug 2 (a hard capsule preparation containing 1 mg of Compound 4 and 30 mg of calcium carbonate (heavy)) and Test drug 3(a hard capsule preparation containing 1 mg of Compound 4 and 30 mg of sofalcone) were nasally administered to 3 rhesus monkeys that were each fixed on the monkey chair without anesthesia using a nasal dropper (Jetlizer: manufactured by Unisiajex Co.), and the sleep-inducing action was observed (record by videotape) for an hour after the administration.

One week later, the behaviors in the control period of the same monkeys were observed.

Results

In each case of the test drug, the sleep-inducing actin was definitely observed in 2 monkeys out of 3 (6 monkeys out of 9) in a period of from 5 to 15 minutes after the nasal administration, followed by drowsy stages.

On the other hand, no particular change was observed in the control group.

Experiment 2

[Sleep-inducing Test by Cisternal Administration]

Method

Three male rhesus monkeys weighing 3.6-4.4 kg were individually placed in cages, and the behaviors of the animals were recorded by videotape for an hour before administration of the drug and for 5 hours after administration of the drug. Compound 32 and prostaglandin D₂ methyl ester (PGD₂) were each dissolved in saline solution and sterilized through a Millipore filter. The drugs were infused cisternally to the monkeys anesthetized with isohalothane inhalation. The doses were 1 μg and 10 μg/0.1 ml/monkey. The same doses of the vehicle were infused cisternally to give a control group. The test was carried out according to the following test schedule.

Week 1: Group treated with vehicle

Week 2: Group treated with 1 μg of Compound 32/monkey

Week 3: Group treated with 10 μg of Compound 32/monkey

Week 4: Group treated with 10 μg of PGD₂/monkey

To determine the sleep, the period for which the monkey closed both eyes was measured at intervals of 15 minutes by playing back the recorded videotape, and the results were scored according to the following scales.

Score Sleep time (15 minutes) 0  0-60 seconds 1  60-225 seconds 2 225-450 seconds 3 450-675 seconds 4 675-900 seconds

Results

Ninety minutes, 135-150 minutes and 210-240 minutes after the administration, the vehicle-treated group was observed to take the weak sleep. In the group treated with 1 μg of Compound 32/monkey, the significant sleep action was observed 30-75 minutes after the administration when compared with the group treated with vehicle (FIG. 1). In the group treated with 10 μg of Compound 32/monkey, the significant sleep action was observed 45 minutes to 5 hours after the administration when compared with the group treated with vehicle (FIG. 1). The transient sleep action was observed in the group treated with 10 μg of PGD₂/monkey 45 minutes after the administration (FIG. 2).

Experiment 3

[Sleep-inducing Action By Cisternal Administration]

Brain wave was recorded according to the method described in the literature (H. ONOE, Proc. Natl. Acad. Sci., 1988, Vol. 185, p.4082).

Method

Four male crab-eating monkeys weighing 3.0 kg-4.7 kg were used. For a chronic implantation of electrodes, surgical operation was aseptically performed under pentobarbital anesthesia, stainless steel screw electrodes were placed on the cerebral cortex and the occipital lobe, and stainless electrodes for electromyogram were placed on the cervical muscles, followed by soldering a lead of a telemetory system transmitter (TL10M3-D70-EEE, Data Sciences, Inc.). The transmitter was subcutaneously implanted into the posterior cervix. After the operation, the operative wound healed completely, and brain wave became stable, then the animals served for the test.

The cerebrospinal fluid was identified by insertion of a spiral needle into the cerebellomedullary cistern from the occipital region under sevoflurane-inhalation anesthesia, after which the test drug (isotonic sodium chloride solution of Compound 32 sterilized through a Millipore filter) was cerebellomedullary-cisternally administered in the amount of 10 μg/0.1 ml/monkey.

Brain wave (EEG) was continuously recorded by a data recorder using a telemetry system (UA-10, Data Sciences, Inc.) for 4 hours after the administration of the test substance, and the behaviors were observed by a video recording system. The changes of sleep-wake stages (wake, non-REM sleep and REM sleep) with time were observed by the changes of brain wave, electromyogram and behavior. And the wake, non-REM sleep, REM sleep times, and the frequency of REM sleep were determined in a period of from 20 minutes to 240 minutes after the administration of the test substance, and results are shown in Table 2.

TABLE 2 Time (sec.) Non-REM Frequency of Wake sleep REM sleep REM sleep Vehicle-treated 185 ± 14  52 ± 12 2.9 ± 2.5 9.5 Group Drug-treated 119 ± 19 106 ± 11 15.2 ± 11.2 25.0* Group *p < 0.05 (to vehicle-treated group) 

What is claimed is:
 1. A sleep-inducing preparation which comprises as an effective ingredient a prostaglandin derivative represented by Formula (I):

wherein X is a halogen atom, Y is a group represented by (CH₂)_(m), a cis-vinylene group or a phenylene group, Z is an ethylene group, a trans-vinylene group, OCH₂ or S(O)_(n)CH₂, R¹ is a C₃₋₁₀ cycloalkyl group, a C₃₋₁₀ cycloalkyl group substituted with C₁₋₄ alkyl group(s), a C₄₋₁₃ cycloalkylalkyl group, a C₅₋₁₀ alkyl group, a C₅₋₁₀ alkenyl group, a C₅₋₁₀ alkynyl group or a bridged cyclic hydrocarbon group, R² is a hydrogen atom, a C₁₋₁₀ alkyl group or a C₃₋₁₀ cycloalkyl group, m is an integer of 1 to 3, and n is 0, 1 or 2, or a pharmaceutically acceptable salt thereof.
 2. The sleep-inducing preparation according to claim 1 which comprises as an effective ingredient the prostaglandin derivative represented by Formula (I) wherein X is a chlorine atom or a bromine atom, Y is a group represented by (CH₂)_(m) or a cis-vinylene group, Z is an ethylene group, a trans-vinylene group, OCH₂ or S(O)_(n)CH₂, R¹ is a C₃₋₁₀ cycloalkyl group or a C₄₋₁₃ cycloalkylalkyl group, R² is a hydrogen atom or a C₁₋₁₀ alkyl group, m is an integer of 1 to 3, and n is 0, 1 or 2, or a pharmaceutically acceptable salt thereof.
 3. The sleep-inducing preparation according to claim 2 which comprises as an effective ingredient the prostaglandin derivative represented by Formula (I) wherein Z is OCH₂, or the pharmaceutically acceptable salt thereof.
 4. The sleep-inducing preparation according to claim 2 which comprises as an effective ingredient the prostaglandin derivative represented by Formula (I) wherein Z is SCH₂, or the pharmaceutically acceptable salt thereof.
 5. The sleep-inducing preparation according to claim 2 which comprises as an effective ingredient the prostaglandin derivative represented by Formula (I) wherein Y is a group represented by (CH₂)_(m), Z is SCH₂, R¹ is a C₃₋₁₀ cycloalkyl group, or the pharmaceutically acceptable salt thereof.
 6. A method for sleep-inducing comprising administering a pharmaceutically effective amount of a prostaglandin derivative represented by Formula (I):

wherein X is a halogen atom, Y is a group represented by (CH₂)_(m), a cis-vinylene group or a phenylene group, Z is an ethylene group, a trans-vinylene group, OCH₂ or S(O)_(n)CH₂, R¹ is a C₃₋₁₀ cycloalkyl group, a C₃₋₁₀ cycloalkyl group substituted with C₁₋₄ alkyl group(s), a C₄₋₁₃ cycloalkylalkyl group, a C₅₋₁₀ alkyl group, a C₅₋₁₀ alkenyl group; a C₅₋₁₀ alkynyl group or a bridged cyclic hydrocarbon group, R² is a hydrogen atom, a C₁₋₁₀ alkyl group or a C₃₋₁₀ cycloalkyl group, m is an integer of 1 to 3, and n is 0, 1 or 2, or a pharmaceutically acceptable salt thereof to a human. 